Crosstalk filtering arrangement with variable frequency filtering to remove effects of FM carrier

Abstract

The effects of crosstalk of an FM carrier from a first signal channel into a second signal channel are reduced by a variable-frequency notch filter coupled in the second channel. The frequency of the notch in the transmission characteristic of the filter is controlled to track the frequency of the FM carrier. Signals in the second channel at the frequency of the FM carrier are attenuated, and therefore the crosstalk signal is attenuated and its effects reduced.

What is claimed is: 
     
       1. An improved two-channel arrangement comprising: a first signal channel carrying a frequency-modulated carrier signal;   a second signal channel;   coupling means coupling said first and second signal channels together whereby said frequency-modulated carrier signal appears in said second signal channel;   wherein the improvement comprises   variable-frequency filter means coupled to said first and second signal channels for filtering from said second signal channel signals at the instantaneous frequency of said frequency-modulated carrier signal.   
     
     
       2. An arrangement according to claim 1, wherein said coupling means is a stray inductive coupling. 
     
     
       3. An arrangement according to claim 1, wherein said variable-frequency filter means comprises a transversal filter. 
     
     
       4. An arrangement according to claim 1, wherein said variable-frequency filter comprises variable delay means coupled in said second signal channel, the delay of said variable delay means being controlled by the frequency of said frequency-modulated carrier signal. 
     
     
       5. An arrangement according to claim 4, wherein the delay of said variable delay means is an integral multiple of the duration of half of a single cycle of said frequency-modulated carrier signal. 
     
     
       6. An arrangement according to claim 5, wherein said integral multiple is one. 
     
     
       7. An arrangement according to claims 4, 5 or 6, wherein said variable-frequency filter further comprises summing means coupled in said second signal channel; and wherein an output of said variable delay means is coupled to an input of said summing means to filter from said second channel said frequency-modulated carrier signal.   
     
     
       8. A television playback apparatus for playing back a record comprising two channels, a first channel of which includes desired first information and a second channel of which includes frequency-modulated second information, comprising: first and second playback means adapted for reproducing said first and second information, said first channel being subject to distortion resulting from crosstalk of said frequency-modulated second information; and   variable-frequency filter means coupled to said first and second playback means for filtering from said first channel in a tracking relationship at least those signals at the frequency of said frequency-modulated carrier.   
     
     
       9. An apparatus according to claim 8, wherein said variable-frequency filter means comprises a variable-frequency transversal filter. 
     
     
       10. An apparatus according to claim 9, wherein said transversal filter comprises a charge-transfer delay device. 
     
     
       11. An apparatus according to claim 10, wherein said charge-transfer delay device is a charge-coupled device. 
     
     
       12. An apparatus according to claim 11 further comprising signal processing means coupling said second channel to said charge-coupled device for clocking said charge-coupled device in response to said frequency-modulated information. 
     
     
       13. An apparatus according to claim 12, wherein said signal processing means comprises frequency multiplication means for multiplying the frequency of said frequency-modulated second information by a first integer; and wherein said charge-coupled device includes a number of cells equal to a second integer multiple of half of said first integer. 
     
     
       14. An apparatus according to claim 12, wherein said signal processing means comprises frequency multiplication means for multiplying the frequency of said frequency-modulated second information by four, and wherein said charge-coupled device includes two cells. 
     
     
       15. An apparatus according to claim 8 wherein said first information is television luminance and said second information is television chrominance.